1. Field of the Invention
This invention relates to a cleaning device in an image forming apparatus utilizing the electrostatic photographic process.
2. Description of the Prior Art
In an image forming apparatus wherein a transferrable image by toner is electrostatically formed on the surface of an endlessly moving image bearing member and the transferrable image is transferred to a transfer material such as paper, whereafter toner remaining on the surface of the image bearing member and foreign materials such as minute paper pieces produced from the transfer paper and adhering to the surface of the image bearing member, rosin, talc, etc. precipitated from the transfer paper or corona products produced by a high voltage generating member in the image forming process are removed to make the image bearing member available for repetitive use, the provision of cleaning means for removing the above-mentioned residual toner and various foreign materials is a requisite condition for obtaining hard copies of good quality.
As the cleaning means for such purpose, there have heretofore been proposed various means using a fur brush, a cleaning blade, a web or the like, and these conventional cleaning means can remove the residual toner but is insufficient to remove the talc, rosin, etc. present in transfer paper pieces or the corona products based on the presence of a high voltage source, and if such materials adhere to the surface of the image bearing member, particularly in the case of high humidity, these substances absorb the moisture and the surface of the image bearing member becomes lower in resistance, and this had led to the undesirable possibility that the electrostatic latent image formed on the surface of the image bearing member is remarkably disturbed (the flow of the image) and the quality of the copy image is remarkably deteriorated. That is, if the electrical resistance on the surface of the image bearing member is low, the flow of the image becomes liable to occur.
To avoid such disadvantages, a device as shown, for example, in FIG. 1 of the accompanying drawings has already been proposed (Japanese Patent Application Laid-Open No. 104970/1982. This device will hereinafter be described briefly. A cleaning device C disposed in proximity to a cylindrical photosensitive medium rotatable in the direction of the arrow is provided with a cleaning blade for scraping off residual toner or the like, a magnetic roller M for catching and conveying the scraped-off toner, and a scraper S disposed in opposed relationship with the magnetic roller M. For example, by setting the spacing between the photosensitive medium 1 and the magnetic roller M to 0.8 mm and the spacing between the magnetic roller M and the scraper S to the order of 0.3 to 0.7 mm, a magnetic brush TB is formed on the surface of the magnetic roller on that side thereof which is more adjacent to the photosensitive medium than the scraper S, whereby the magnetic brush removes the residual toner or the like conveyed while adhering to the surface of the photosensitive medium 1. Such a device is effective to remove paper powder of 0.1 to 1 mm having a relatively weak adhesion force with respect to the photosensitive medium, but it has been difficult for such device to remove substances having a strong adhesion force such as rosin, talc and corona products.
Further, in order to avoid such a disadvantage, there has already been proposed cleaning means in which an elastic roller rotates while being in frictional contact with the surface of an image bearing member (U.S. Pat. No. 3,838,472 corresponding to Japanese Patent Application Laid-Open No. 100585/1980), but if a sponge roller is used, toner spills or scatters from the portion of frictional contact and causes clogging, which has unavoidably led to a deteriorated cleaning effect. Also, if the roller is too strongly urged against the image bearing member, residual toner is conversely pressed against the surface of the image bearing member to thereby form a portion of high resistance, which has led to the undesirable possibility that unnecessary developing action is effected to adversely affect the quality of image of hard copies. Further, if the roller is rotated while being in strong contact with the surface of the image bearing member, the required torque of the driving system is increased, and this has caused image blur. Also, if a roller of low hardness is used to alleviate the frictional action, the surface of the image bearing member is damaged because, for example, in the case of polyurethane rubber, an aging preventing agent is used, and in the case of silicone rubber, not only a roller of low hardness is difficult to manufacture, but also there has been the undesirable possibility that the residue of unreacted silicone oil or the like injures the surface of the image bearing member.